All Downloads are FREE. Search and download functionalities are using the official Maven repository.

soot.dava.toolkits.base.AST.transformations.LocalVariableCleaner Maven / Gradle / Ivy

Go to download 

package soot.dava.toolkits.base.AST.transformations;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 2005 Nomair A. Naeem
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;

import soot.Local;
import soot.Value;
import soot.dava.DavaBody;
import soot.dava.DecompilationException;
import soot.dava.internal.AST.ASTMethodNode;
import soot.dava.internal.AST.ASTNode;
import soot.dava.internal.AST.ASTStatementSequenceNode;
import soot.dava.internal.asg.AugmentedStmt;
import soot.dava.toolkits.base.AST.analysis.DepthFirstAdapter;
import soot.dava.toolkits.base.AST.traversals.ASTParentNodeFinder;
import soot.dava.toolkits.base.AST.traversals.ASTUsesAndDefs;
import soot.jimple.Constant;
import soot.jimple.DefinitionStmt;
import soot.jimple.Stmt;

//import soot.dava.internal.javaRep.*;
//import soot.dava.toolkits.base.AST.structuredAnalysis.*;

/**
 * The class is aimed to target cleaning up of unused local variables. Should be invoked after executing CopyPropagation
 *
 * Another thing that this class does which perhaps should have been implemented separately is to check whether there is an
 * assignment which never gets used later on. If there exists such an assignment this assignment is removed first and then
 * all the useless locals checks should be reapplied (until a fixed point)
 */

public class LocalVariableCleaner extends DepthFirstAdapter {
  public final boolean DEBUG = false;

  ASTNode AST;

  ASTUsesAndDefs useDefs;

  ASTParentNodeFinder parentOf;

  public LocalVariableCleaner(ASTNode AST) {
    super();
    this.AST = AST;
    parentOf = new ASTParentNodeFinder();
    AST.apply(parentOf);
  }

  public LocalVariableCleaner(boolean verbose, ASTNode AST) {
    super(verbose);
    this.AST = AST;
    parentOf = new ASTParentNodeFinder();
    AST.apply(parentOf);
  }

  /*
   * Get all locals declared in the method If the local is never defined (and hence never used) remove it If the local is
   * defined BUT never used then you may remove it IF AND ONLY IF The definition is either a copy stmt or an assignment of a
   * constant (i.e. no side effects)
   */
  public void outASTMethodNode(ASTMethodNode node) {
    boolean redo = false;

    useDefs = new ASTUsesAndDefs(AST); // create the uD and dU chains
    AST.apply(useDefs);

    // get all local variables declared in this method
    Iterator decIt = node.getDeclaredLocals().iterator();

    ArrayList removeList = new ArrayList();
    while (decIt.hasNext()) {
      // going through each local declared

      Local var = (Local) decIt.next();

      List defs = getDefs(var);

      // if defs is 0 it means var never got defined
      if (defs.size() == 0) {
        // var is never defined and hence is certainly not used anywhere
        removeList.add(var);
      } else {
        // if a var is defined but not used then in some conditions we can remove it

        // check that each def is removable
        Iterator defIt = defs.iterator();

        while (defIt.hasNext()) {
          DefinitionStmt ds = defIt.next();

          if (canRemoveDef(ds)) {
            // if removeStmt is successful since something change we need to redo
            // everything hoping something else might be removed....
            // in this case method returns true
            redo = removeStmt(ds);
          }
        } // while going through defs

      } // end else defs was not zero
    } // going through each stmt

    // go through the removeList and remove all locals
    Iterator remIt = removeList.iterator();
    while (remIt.hasNext()) {
      Local removeLocal = remIt.next();
      node.removeDeclaredLocal(removeLocal);

      /*
       * Nomair A. Naeem 7th Feb 2005 these have to be removed from the legacy lists in DavaBody also
       *
       */
      // retrieve DavaBody
      if (AST instanceof ASTMethodNode) {
        // this should always be true but whatever
        DavaBody body = ((ASTMethodNode) AST).getDavaBody();
        if (DEBUG) {
          System.out.println("body information");
          System.out.println("Control local is: " + body.get_ControlLocal());
          System.out.println("his locals are: " + body.get_ThisLocals());
          System.out.println("Param Map is: " + body.get_ParamMap());
          System.out.println("Locals are:" + body.getLocals());
        }
        Collection localChain = body.getLocals();
        if (removeLocal != null && localChain != null) {
          localChain.remove(removeLocal);
        }
      } else {
        throw new DecompilationException("found AST which is not a methodNode");
      }

      if (DEBUG) {
        System.out.println("Removed" + removeLocal);
      }
      redo = true;
    }

    if (redo) {
      // redo the whole function
      outASTMethodNode(node);
    }
  }

  /*
   * A def can be removed if and only if: 1, there are no uses of this definition 2, the right hand size is either a local or
   * a constant i.e. no need to worry about side effects
   */
  public boolean canRemoveDef(DefinitionStmt ds) {
    List uses = useDefs.getDUChain(ds);

    if (uses.size() != 0) {
      return false;
    }

    // there is no use of this def, we can remove it if it is copy stmt or a constant assignment
    if (ds.getRightOp() instanceof Local || ds.getRightOp() instanceof Constant) {
      return true;
    }

    return false;
  }

  /*
   * This method looks up all defs and returns those of this local
   */
  public List getDefs(Local var) {
    List toReturn = new ArrayList();

    HashMap dU = useDefs.getDUHashMap();
    Iterator it = dU.keySet().iterator();
    while (it.hasNext()) {
      DefinitionStmt s = (DefinitionStmt) it.next();
      Value left = s.getLeftOp();
      if (left instanceof Local) {
        if (((Local) left).getName().compareTo(var.getName()) == 0) {
          toReturn.add(s);
        }
      }
    }
    return toReturn;
  }

  public boolean removeStmt(Stmt stmt) {
    Object tempParent = parentOf.getParentOf(stmt);
    if (tempParent == null) {
      // System.out.println("NO PARENT FOUND CANT DO ANYTHING");
      return false;
    }

    // parents are always ASTNodes, hence safe to cast
    ASTNode parent = (ASTNode) tempParent;

    // REMOVING STMT
    if (!(parent instanceof ASTStatementSequenceNode)) {
      // parent of a statement should always be a ASTStatementSequenceNode
      return false;
    }
    ASTStatementSequenceNode parentNode = (ASTStatementSequenceNode) parent;

    ArrayList newSequence = new ArrayList();
    int size = parentNode.getStatements().size();
    for (AugmentedStmt as : parentNode.getStatements()) {
      Stmt s = as.get_Stmt();
      if (s.toString().compareTo(stmt.toString()) != 0) {
        // this is not the stmt to be removed
        newSequence.add(as);
      }
    }
    // System.out.println("STMT REMOVED---------------->"+stmt);
    parentNode.setStatements(newSequence);
    if (newSequence.size() < size) {
      return true; // size of new node is smaller than orignal size
    }

    return false;// didnt actually delete anything for some weird reason...shouldnt happen
  }

}
 















© 2015 - 2024 Weber Informatics LLC | Privacy Policy